puzzles This multiple choice probability puzzle has been causing arguments for years Mark Frauenfelder
useful stuff Excellent cheap puzzle book: The Moscow Puzzles: 359 Mathematical Recreations Mark Frauenfelder
puzzles Can we wrap a 1x1x1 cube with the blue 3×3 piece of paper, cutting along some edges without disconnecting it? Mark Frauenfelder
brain teasers Saturday morning mind-benders: "Newcomb's Problem" and "Parfit's Hitchhiker" dilemma Mark Frauenfelder
Boing Boing Shop This awesome DIY 3D marble maze is the perfect gift for brain teaser fans – grab it for less than $26 today Boing Boing's Shop